AV POPULAR PHYSICS. 9 



The center of gravity falls steadily 16.08 feet, whatever 

 other force may act on the body. 



(See Second Law of Motion.) 



48. If one is riding rapidly, in which direction will he 

 be thrown when the horse is suddenly stopped ? 



In the same direction in which he is going. He has the 

 motion of the carriage, and his momentum carries him for- 

 ward. 



49. When standing in a boat, why, as it starts, are we 

 thrown backivard ? 



Because our bodies tend to remain stationary, while the 

 boat carries our feet forward. 



50. When carrying a cup of tea, if we move or stop 

 quickly, why is the liquid liable to spill ? 



The momentum of the tea tends to keep it still or in mo- 

 tion, as the case may be. If we move the cup quickly, the 

 motion is not imparted to the liquid soon enough to overcome 

 this momentum. "When, therefore, we start, the tea spills out 

 backward ; or, when we stop, it spills out forward. We under- 

 stand this if we can tell why a cup of tea is more liable to 

 spill than one of sugar. 



51. Why, when closely pursued, can we escape by dodg- 

 ing? 



"We turn sharply. Our pursuer, ignorant of our design, can 

 not overcome his momentum so as to turn as quickly, and 

 hence is carried past. 



52. WJiy is a carriage or sleigh, 'when sharply turning 

 a corner, liable to tip over ? 



Because its, momentum tends to carry it directly forward. 



53. Wiiy, if you place a card on your finger, and on top 

 of it a cent, can you snap the card from under the cent 

 without knocking tJie latter off your finger ? 



Because the friction between the card and the cent is so 

 slight that, by a quick snap, you can give motion to the former 

 without affecting the latter enough to make it fall off. 



